AutoHiding toolWindow causing exception

 Hi,

I having a hard time with ToolWindows. Let me explain. I have an application with autohide right and left containers. They are ToolWindows. And I create dynamically custom userControls(gauge elements). When custom userControl is created, I need set up it's properites. For that in a toolWindow on the right side I have property gird. Here is a code of right toolWindow with property grid in xaml:

<docking:DockSite.AutoHideRightContainers>
    <docking:ToolWindowContainer x:Uid="ToolWindowAutoRight" docking:DockSite.ControlSize="300,300" x:Name="ToolWindowAutoRight">
        <docking:ToolWindow x:Uid="ToolBoxEigenschaften" Title="{DynamicResource Eigenschaften}" ImageSource="/Resources\png\Toolbox16.png" x:Name="ToolBoxEigenschaften" 
                                            CanClose="False" HasOptions="False" >
            <DockPanel HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Dock="Right">
                <DockPanel HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Dock="Top" >
                    <Grid>
                        <Button Name="SaveBtn" Content="    Save    " Command="{Binding SaveClickCommand}"/>
                        <Button Name="EditBtn" Content="    Edit    " Command="{Binding EditClickCommand}"/>
                        <Button Name="CancelBtn" Content="   Cancel   " Command="{Binding CancelClickCommand}"/>
                    </Grid>
                </DockPanel>
                
                <DockPanel HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Dock="Bottom">
                    <shared:PixelSnapper  x:Uid="shared:PixelSnapper_1" HorizontalRoundMode="Floor" VerticalRoundMode="Floor">
                        <propgrid:PropertyGrid x:Uid="PropertiesUserControl" x:Name="PropertiesUserControl"  IsSummaryVisible="True" AreNestedCategoriesSupported="True" 
                                            IsEnabled="True" AreDefaultSortDescriptionsEnabled="False" IsReadOnly="{Binding IsReadOnly}" 
                                            AreCategoriesAutoExpanded="False" SelectedObject="{Binding SelectedObject}">
                        </propgrid:PropertyGrid>
                    </shared:PixelSnapper>
                </DockPanel>
            </DockPanel>
        </docking:ToolWindow>                       
    </docking:ToolWindowContainer>
</docking:DockSite.AutoHideRightContainers>

 Untill now everything is working. When I have several userControls I want to navigate among them, and when userControl isSelected, if rigth side toolWindow is opened, I want to autoHide it. For this I have code in codeBehind :

C# private void OnHidePropertyGrid()
   {
        if (ToolBoxEigenschaften.CheckAccess())
        {
            ToolBoxEigenschaften.AutoHide(); //exception while executing this line        
        }
   }

 Now during execution of this code, I get - Exception: Caught: "EnumConverter cannot convert from (null)." (System.NotSupportedException) Exception Message = "EnumConverter cannot convert from (null).", Exception Type = "System.NotSupportedException", Exception WinRT Data = "" .

Why do I get this line and how can I fix it? This is first issue.

On the left side I also have several toolWindows.

They all are like this one:

<docking:ToolWindow x:Uid="ToolBoxAlarme"  Title="{DynamicResource Alarme}" x:Name="ToolBoxAlarme"      
       CanClose="False" HasOptions="False" local:ToolWindowTabFlashBehavior.IsFlashing="{Binding AlarmIsFlashing}"
       local:ToolWindowTabFlashBehavior.IsStoppedWhenActivated="False">

       <DockPanel HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Dock="Top">
           <ListBox x:Name="AlarmeListBox" IsSynchronizedWithCurrentItem="True" ItemsSource="{Binding ListAlarms}">
               <ListBox.ItemTemplate>
                   <DataTemplate>
                       <TextBlock Text="{Binding}"/>
                   </DataTemplate>
               </ListBox.ItemTemplate>
           </ListBox>
       </DockPanel>
</docking:ToolWindow>

 Here ListAlarms it is an observableCollection of type <string>. And the issue is that when this toolWindow is Activated, after some period of time I get ArgumentOutOfRangeException "Index was out of range. Must be non-negative and less than the size of the collection." and my program terminates.

In debug mode CallStack is not pointing to code. So I would like to know, may be I implemented toolWindow in a wrong way and it is causing this error or it's somewhere else?

Thank you in advance.